linux-kernel - Re: [EXTERNAL] Re: [PATCH] arm: dts: am437x-sk-evm: add wilink8 support

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Message-ID: <20180503141759.GP98604@atomide.com>
Date:   Thu, 3 May 2018 07:17:59 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     "Reizer, Eyal" <eyalr@...com>
Cc:     Eyal Reizer <eyalreizer@...il.com>,
        "bcousson@...libre.com" <bcousson@...libre.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH] arm: dts: am437x-sk-evm: add wilink8
 support

* Reizer, Eyal <eyalr@...com> [180503 06:43]:
> > 
> > * Eyal Reizer <eyalreizer@...il.com> [180501 00:26]:
> > > enable mmc3 used for wlan and uart1 used for bluetooth
> > > configure the gpios used for wlan and bluetooth controls
> > > add fixed voltage regulator used for wlan power control
> > ...
> > >  / {
> > >  	model = "TI AM437x SK EVM";
> > > @@ -158,6 +159,22 @@
> > >  			};
> > >  		};
> > >  	};
> > > +
> > > +	vmmcwl_fixed: fixedregulator-mmcwl {
> > > +		/*
> > > +		 * WL_EN is not SDIO standard compliant. It is an out of band
> > > +		 * signal and hard to be dealt with in a standard way by the
> > > +		 * SDIO core driver.
> > > +		 * So modelling the WL_EN line as a regulator was a natural
> > > +		 * choice as the MMC core already deals with MMC supplies.
> > > +		 */
> > > +		compatible = "regulator-fixed";
> > > +		regulator-name = "vmmcwl_fixed";
> > > +		regulator-min-microvolt = <1800000>;
> > > +		regulator-max-microvolt = <1800000>;
> > > +		gpio = <&gpio4 8 GPIO_ACTIVE_HIGH>;
> > > +		enable-active-high;
> > > +	};
> > >  };
> > 
> > Interesting that it needs much longer delay here compared to the
> > earlier?
> 
> Where do you see a delay in here?
> There is no startup-delay-us value used in this patch.

Oops sorry, I misread the voltage above as the startup-delay-us
value :)

> > BTW, I do have a patch in work to add pwrseq support for wlcore that
> > allows leaving out the regulator here. It still needs a bit more
> > work though.
> > 
> > And I also have a series in work to make wlcore use runtime PM that
> > needs even more work, just FYI to avoid any duplicate work.
> > 
> > Hmm you don't happen to have a patch series somewhere making
> > wlcore use the SDIO dat lien interrupt?
> wilink has always used out of band interrupt (using wlan_irq gpio).
> in-band interrupts was not supported.
> See section 10.5.2 in this the wl18xx hardware integration guide:
> http://www.ti.com/lit/ug/swru437/swru437.pdf

Hmm yeah I've been wondering about that. Why not follow the SDIO
standard here though? Do you have links to documentation explaining
that?

> > I think we should use that when idle rather than the (edge) gpio
> > interrupt as the SDIO dat interrupt is level sensitive and wired
> > to the always on gpio bank for most SDIO controller instances.
> > On runtime PM wakeup, there's no status anywhere to been with the
> > GPIO edge interrupt.
> > 
> I agree that it would have been better, especially for cases such as wake 
> On wlan, but again, in-band interrupt was something that was talked 
> about way back but it was never implemented.

I think we can have both if performance is the reason for the
out of band interrupt. We could still use SDIO dat line interrupt
during idle for wake-up events.

Regards,

Tony